Methods for fluid contacting in a downflow vessel

ABSTRACT

A contacting device and method are presented for the collection, contacting, and distribution of fluids between particulate beds of a downflow vessel, which may operate in co-current flow. By one approach, the contacting device includes a liquid collection tray, a mixing channel in fluid communication with the liquid collection tray, and a liquid distribution zone.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Provisional Application No.62/538,246 filed Jul. 28, 2017, the contents of which cited applicationare hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

This invention relates to methods for contacting fluids in a co-currentflow vessel. More particularly, the invention relates to methods forcontacting liquid and vapor between two beds in a downflow vessel.

BACKGROUND OF THE INVENTION

A wide variety of processes use co-current flow reactors, where a fluidor fluids flow over a solid bed of particulate materials, to provide forcontact between the fluid and solid particles. In a reactor, the solidmay comprise a catalytic material on which the fluid reacts to form aproduct. The fluid can be a liquid, vapor, or mixture of liquid andvapor, and the fluid reacts to form a liquid, vapor, or a mixture of aliquid and vapor. The processes cover a range of processes, includinghydrocarbon conversion, gas treatment, and adsorption for separation.

Co-current reactors with fixed beds are constructed such that thereactor allows for the fluid to flow over the catalyst bed. When thefluid is a liquid, or liquid and vapor mixture, the fluid is usuallydirected to flow downward through the reactor. Multibed reactors arealso frequently used, where the reactor beds are stacked over oneanother within a reactor shell. Typically, they are stacked with somespace between the beds.

The interbed spaces are often created to provide for intermediatetreatment of the process fluid, such as cooling, heating, mixing andredistribution.

In exothermic catalytic reactions, the control of fluid temperature anddistribution is important. The temperature and composition of the fluidsfrom an upper catalyst bed and from outside of reactor should be wellmixed before being distributed to the lower catalyst bed. Initial poortemperature and composition distribution at top of a catalyst bed canpersist or grow as the process fluids move down the reactor. Hot spotscan develop and cause rapid deactivation of the catalyst and shorten thereactor cycle length. The space between catalyst beds is for theinjection of a quench gas or liquid and for fluid mixing anddistribution. In hydrocarbon processing, the quench gas is often a coolhydrogen/hydrocarbon stream. However, cooling a fluid withoutcontrolling the mixing and distribution leads to uneven reactions anduneven temperature distribution in subsequent reactor beds. And complexmixing and distribution systems takes up valuable space in a reactorchamber holding multiple catalyst beds.

Due to constraints in the height of the space between reactor beds,there is a limited amount of space for introducing a quench fluid andmixing the vapor and liquid along with the quench fluid. Particularly,for existing hydroprocessing reactors, the space between catalyst bedsis already set, and sometimes it is difficult to install new internalsfor improving mixing of fluids within the existing interbed spacewithout reducing the height of catalyst beds. Even for new reactors, itis often desired to reduce the overall size of the reactors to reducecapital expenditure and the profile of the reactor in a processingplant. Therefore, it is desirable to provide for good mixing of fluidsbetween adjacent catalyst beds in a relatively short interbed space.

Previous attempts to overcome these limitations have included vortex orturbulent type mixers which generally include providing flow of thefluids together in a manner to affect mixing. An example of a vortextype mixer is described in U.S. Pat. No. 8,017,095. The cylindricalmixing device 40 is positioned on a collecting tray and includes inlets50 and 55 and a single outlet 80 in the bottom center of the bottomwall. The fluid and liquid enter the device together through inlets 50and 55. These devices are limited in that mixing is affected by theturbulent or swirling flow of fluids together within the device in thesame general direction and with vapor atop of liquid.

The design of reactor internals to overcome these limitations can savesignificantly on the valuable space within a reactor. New reactorinternals that improve the utilization of the space within a reactorshell can maximize catalyst loading, and obviate the need for newreactor shell components, as well as prevent the down time for replacingan entire reactor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional side view of a mixing device situated withina multi-bed catalytic reactor in accordance with various embodiments;

FIG. 2A is a cross-sectional top view of a mixing device in accordancewith various embodiments;

FIG. 2B is a side view of a vapor chimney of the mixing device of FIG. 2in accordance with various embodiments;

FIG. 3 is a partial perspective view of a mixing device in accordancewith various embodiments;

FIG. 4 is a partial perspective view of an alternative mixing device inaccordance with various embodiments;

FIG. 5 is a cross-sectional side view of an alternative mixing devicesituated within a multi-bed catalytic reactor in accordance with variousembodiments;

FIG. 6 is a cross-sectional top view of an alternative mixing device inaccordance with various embodiments;

FIG. 7 is a partial perspective view of an alternative mixing device inaccordance with various embodiments;

FIG. 8 is a cross-sectional side view of an alternative mixing devicesituated within a multi-bed catalytic reactor hand having a distributorbottom tray offset below the mixing device in accordance with variousembodiments;

FIG. 9 is a cross-sectional side view of a mixing device illustrating atop plate in accordance with various embodiments;

FIG. 10 is a cross-sectional top view of a mixing device illustrating atop plate in accordance with various embodiments; and

FIG. 11 is a side view of a weir of a top plate in accordance withvarious embodiments.

DETAILED DESCRIPTION OF THE INVENTION

According to various aspects, the mixing device and system, and methodfor using the same, disclosed herein are disposed in the space betweenbeds in a co-current flow vessel. For ease of explanation the followingwill be described in terms of a downflow reactor including two or morespaced catalyst beds, but the mixing devices and system, and methodsdescribed herein may also be used in and applied to other hydrocarbonprocessing vessels having different types of processing beds, including,but not limited to adsorbent beds in an adsorbent separation chamber.The catalyst beds in a reactor are separated by space for quench, mixingand distribution of the fluids, where the mixing zones are designed tocool/heat, mix, and sometimes condense effluent fluids from a catalystbed above. In one example, as illustrated in FIG. 1, the mixing deviceand system may be included in a hydroprocessing downflow reactor 5 andfluid flows from superior catalyst bed 10 to an inferior catalyst bed15. The fluid may include vapor, liquid, or a mixture of vapor andliquid. The reactor fluid may be quenched with a quench gas or liquid(collectively referred to as “quench fluid” herein) from a quench fluiddistributor 20, and the fluid is mixed and then distributed to theinferior catalyst bed 15 in quench zone 25. It should be noted that theterm “fluid” as used herein refers to either or both of liquid andvapor. The fluid is mixed to minimize temperature and compositiondifferences before being distributed to the inferior catalyst bed 15below the quench zone. In current systems, there is considerable spacebetween the reactor beds for quench and mixing. A reduction in theamount of space needed for these functions can advantageously providefor maximum catalyst loading within the reactor 5 to improve processingand performance without replacing an entire reactor. Similarly, newreactors may be designed with smaller profiles and at smaller capitalexpense if the height of quench zones is minimized.

Good distribution of liquids over catalyst beds is important to avoidadverse effects, such as uneven temperature rise and hot spots withinthe catalyst bed. Hot spots occurring in the catalyst beds can lead to ashortened catalyst life or to poor product quality. The methods anddevices described herein are designed to reduce the height of quenchzone without sacrificing fluid mixing and distribution performance.

By one aspect, a system 30 is provided for vapor-liquid contacting in aquench zone between catalyst beds in co-current flow reactor 5. In oneexample, the reactor 5 may be a generally cylindrically shaped downflowreactor. The system 30 includes a liquid collection tray 35 that may besupported by a support structure within the reactor 5, for example, asupport ring or other structures not shown. The liquid collection tray35 preferably extends substantially across the area of the reactor 5 torestrict fluids from by-passing the mixing zone 30, and openings aretypically provided through the liquid collection tray 35 to allowdistribution of fluids to the inferior catalyst bed 15. At least aportion of the liquid collection tray 35 collects fluids travelingdownwardly from the superior catalyst bed 10 thereon.

Referring to FIGS. 1-3, a mixing device 40 is provided for mixing liquidand vapor within the quench zone 25. The mixing device is preferablysupported by the liquid collection tray and is positioned thereabove,although the mixing device 40 may be positioned below the liquidcollection tray, or have portions thereof above or below the liquidcollection tray 35. By one aspect, the mixing device 40 is supported onthe liquid collection tray 35 and includes an outer wall 45 separatingthe mixing device 40 from a liquid collection zone 50. The outer wall 45may be generally circular as illustrated or may be polygonal or anothersuitable shape. The liquid collection zone 50 may include a gap betweenthe outer wall 45 and the reactor wall 5 extending entirely or at leasta portion about the outer wall 45. During operation, liquid from thesuperior catalyst bed 10 is collected in the liquid collection zone 50.In one example, in order for the liquid collecting zone to providesufficient space for existing reactor shell attachments, installation ofthe mixing device and for accommodating the quench distributor 20 theouter wall 45 is positioned between about 5 and about 20 in. from thereactor wall. In another example it is between about 10 and about 15 in.from the reactor wall. By one approach, a baffle 51 extends across theliquid collection zone to facilitate flow in a single direction aboutthe mixing device outer wall 45 to improve pre-mixing of the liquid. Asillustrated in FIG. 4, to provide additional mixing area within themixing device 40, by one aspect the outer wall 45 may be positioned inclose proximity or adjacent to the reactor wall 5. In one approach, theouter wall 45 is positioned between about 0 and about 5 in. from thereactor wall. To provide sufficient area for liquid collection, in thisapproach, a liquid collection well 55 may be provided in a gap in theouter wall 45.

The mixing device 40 includes a mixing channel 60 for mixing vapor andliquid. The mixing channel 60 may include one or more elongate channelsto facilitate the flow of liquid and vapor therethrough. Since vaporflows through the mixing channel 60, at least a portion of the mixingchannel 60 is substantially enclosed to maintain vapor within the mixingchannel 60 during mixing. As illustrated in FIG. 2A, the mixing channel60 is an elongate generally annular channel extending about the centeraxis of the reactor 5 and/or the mixing device 40. The annular mixingchannel 60 may be round as illustrated, polygonal or other shapes. Byone aspect the mixing channel 60 is formed between the outer wall 45 andan inner wall 65. The outer wall 45 and inner wall 65 may be formed bybaffles extending upwardly from the mixing channel bottom wall 70, whichmay be a portion of the liquid collection tray. The outer wall 45 andinner wall 65 may include two or more separate baffles as illustrated inFIG. 2A or a single baffle extending in an inwardly swirling pattern.

By one aspect, the mixing channel 60 includes a liquid inlet 75 at aninlet end portion 80 thereof and an outlet 85 at an outlet end portion90 thereof. In one approach the liquid inlet 75 includes an opening 95in the side of the outer wall 45 or other wall of the mixing channel 60at the inlet end portion 80. It should be noted that as used herein, theterm “opening” refers to any type of opening or other structure capableof providing the passage of fluid therethrough, including, but notlimited to apertures, nozzles, perforations, slots, tubes, and spouts.The liquid inlet opening 95 may be positioned at a lower portion of themixing channel 60. In this regard, liquid collected on the liquidcollection tray 35 can enter through the opening 95, however, the lowposition of the opening 95 allows liquid to flow through preferentiallythan vapor. To this end, the liquid inlet opening 95 may be formed witha top portion 96 near or beneath an expected operating liquid levelabove the liquid collection tray 35 at full vapor and liquid designloading. In one example the opening is positioned at a bottom 70% of theheight of the mixing channel 60. In another example, the opening ispositioned at a bottom 50% of the height of the mixing channel 60 and ata bottom 30% of the height of the mixing channel 60 in another example.In one example, at least about 80% of an open area of the liquid inletopening 95 is in a bottom 50% of the height of the mixing channel 60 andin about a bottom 30% of the height of the mixing channel in anotherexample. In this manner, fluid flowing through the liquid inlet iscomprised substantially of liquid. In one approach, at least about 40%of opening is for liquid flow. In another example, at least about 80% ofthe opening is for liquid flow.

Liquid entering the liquid inlet 95 travels through the mixing channel60 and in a generally downstream direction toward the outlet 85. By oneaspect, the mixing device includes one or more vapor inlets for passingvapor from an upper catalyst bed and outside of reactor into the mixingchannel 60. In one approach, a vapor inlet 100 is positioned along themixing channel 60 downstream of the liquid inlet 75 for improvingcontacting of the vapor with the liquid which passes through the mixingchannel 60. A vapor inlet opening 105 may be provided in the outer wall45 of the mixing channel, and may be positioned at a bottom portion ofthe mixing channel 60 to improve vapor-liquid contacting as the vaporenters through the vapor inlet opening 105 even when the level of theliquid flowing through the mixing channel 60 is relatively low. In oneapproach, a mixing channel weir 106 may extend across a portion of themixing channel 60. The weir 106 maintains a minimum amount of liquid inthe mixing channel so that vapor will contact liquid even when only asmall amount of liquid flows through the mixing channel 60, for exampleduring startup or shutdown. The weir can be positioned in various anglesrelative to the mixing channel for improving liquid mixing. In oneexample the opening 105 is positioned at a bottom 70% of the height ofthe mixing channel 60. In another example, the vapor inlet opening 105is positioned at a bottom 50% of the height of the mixing channel 60 andat a bottom 10% of the height of the mixing channel 60 in anotherexample. In one example, at least about 80% of an open area of the vaporinlet opening 105 is in a bottom 50% of the height of the mixing channel60 and in about a bottom 10% of the height of the mixing channel 60 inanother example.

According to one aspect, a vapor chimney 110 surrounds the vapor inletopening 105. The vapor chimney 110 includes a chimney wall that extendsup from the collection tray and includes an upper chimney inlet oropening 115 to provide for passage of vapor into the chimney 110 andthrough the vapor inlet opening 105. The vapor chimney opening 115 maybe at the top of the chimney 110 or an aperture through the chimneywall. Unless specified, as used herein, upper opening refers to one ormore openings that are elevated above a bottom wall or liquid level, forexample the liquid collection tray 35 or a bottom wall of a portion ofthe mixing device 40, and may include, but are not limited to openingsin a top or side of a vapor chimney. The opening 115 is preferablypositioned at a height above the liquid collection tray 35 above anormal operation liquid level to restrict liquid from entering thechimney 110 and through the vapor inlet 100 with the vapor. In oneexample, at least about 60% of the fluid entering vapor inlet 100 isvapor. In another example, at least about 80% of the fluid enteringvapor inlet 100 is vapor.

The vapor inlet opening 105 may include one or more openings through theouter wall 45 of the mixing channel 60 as illustrated in FIGS. 2, 2B and3. Alternatively, according to various aspects, the vapor inlet chimney110 may extend into the mixing channel 60 and the vapor inlet opening105 may be formed in the chimney wall. In any event, the opening 105 isin fluid communication with the mixing channel 60, and vapor enteringthe mixing channel 60 from the vapor inlet opening 105 may be introducedinto the mixing channel 60 generally across the mixing channel 60 andinto and across the liquid stream traveling therethrough. It has beenidentified injecting or dispersing the vapor toward and across theliquid stream in this manner provides improved intimate contact betweenthe vapor and liquid in the channel and improved mixing of the liquidand vapor as compared to introducing the vapor and liquid streams into amixing channel together through a common opening with vapor atop ofliquid. Further, creating a sufficient pressure drop in the vaporchimney causes the vapor to be dispersed into the mixing channel 60 withsufficient velocity and momentum to travel across the downstream flowingfluid stream to improve mixing. In one example, the pressure dropthrough the vapor chimney 110 may be between about 0.2 to about 2.5 psi,between about 0.3 and about 2.0 psi in another example, and betweenabout 0.5 and 1.5 in yet another example.

Further, injecting the vapor into a liquid swirling about an annularmixing channel or a liquid with turbulent flow provides additionalmixing due to the flow of the vapor and liquid together once the vaporhas been introduced. The vapor may be directed through the vaporopenings transversely or obliquely to the mixing channel. As mentioned,by one aspect, as illustrated in FIG. 2B, the vapor inlet may includetwo or more openings 105 positioned at different heights above theliquid collection tray 35. Providing the openings 105 at differentheights allows the optimum contact between vapor and liquid.

While introducing the vapor orthogonally or near orthogonally to theliquid stream flowing therethrough has been shown to provide goodmixing, introducing the vapor in an oblique downstream directionrelative to the mixing channel outer wall 45 may provide good mixingwhile reducing interruption with the flow of fluid in the downstreamdirection. In this regard, by one aspect, baffles 120 may be providedfor directing the vapor entering the mixing channel downstream andobliquely to the liquid stream. The baffles 120 may extend from theopening at an acute angle to the outer wall 45 as illustrated in FIG. 7.In one example the baffles extend generally downstream at an acute angleto the mixing channel outer wall 45. In one example, the acute angle isbetween about 10 and about 60 degrees, and about 20 and about 45 degreesfrom outer wall 45 in another example.

In one aspect, one or more additional vapor inlets 125 having vaporinlet openings are positioned downstream of the liquid inlet 75 atdifferent downstream distances than the first vapor inlet 100. It hasbeen identified that providing two or more vapor inlets at differentpositions along the mixing channel 60 may improve vapor-liquidcontacting by gradually directing the vapor into the liquid stream asthe liquid stream passes through the mixing channel. The additionalvapor inlets 125 may also include vapor chimneys 130 having upperopenings. The heights of the upper chimney openings 115 and 135 of thedifferent vapor chimneys may be different such that a chimney having alower opening height may provide liquid overflow into the vapor chimneyand through the vapor inlet in the event of excess liquid accumulationon the liquid collection tray 35 during operation. By providing otherchimneys having higher upper chimney opening heights above the tray 35,those chimneys may still restrict excess liquid from entering thechimney with the vapor, allowing primarily vapor to pass through thechimney and into the mixing channel, maintaining vapor-liquid contactingtherein. Although various combinations of vapor inlet chimney upperopening heights are possible, preferably an upstream chimney has a lowerlow opening height than a downstream chimney (downstream along themixing channel). In this regard, if the liquid level in the liquidcollection zone rises, the liquid can overflow into the upstream chimneywhile vapor still flows through the downstream chimney to contact theliquid that bypassed the liquid opening and entered the mixing channel60 via the upstream chimney.

As described further below with regard to FIG. 4, by one aspect themixing channel includes an outer mixing channel 136 and an inner mixingchannel 137 positioned inwardly of the outer mixing channel 136. Inaccordance with this aspect, one or more internal vapor inlets 138 maybe provided within the mixing channel to provide vapor to the innermixing channel 137. The internal vapor inlet 138 includes a chimneyvapor opening 139 through a wall of the inner mixing channel 137 orthrough a chimney 142 of the internal vapor inlet. Similar to the vaporinlet 100, the internal vapor inlet opening 139 may be positioned in alower portion of internal mixing channel 137 so that the vapor enteringthe mixing channel 137 through the opening 139 is directed toward theliquid stream flowing therethrough. An internal chimney upper opening143 may extend above the top plate 150 to allow vapor to pass from abovethe top plate through the chimney 142 and into the inner mixing channel137. In one approach, the chimney opening may be positioned above anupper surface of the top plate 150 to restrict liquid from entering thechimney 142 along with vapor.

As mentioned, the mixing channel 60 includes inner and outer walls 65and 45 for defining a fluid passageway. The mixing channel 60 furtherincludes a bottom wall 140 and a top wall 145. The bottom wall 140 mayinclude a portion of the liquid collection tray 35 beneath the mixingchannel. The top wall 145 may be provided in the form of top plate ortray 150 covering at least a portion of the mixing channel 60. In oneapproach, the inner and outer walls 65 and 45 include one or morebaffles attached to and extending upwardly from the liquid collectiontray 35. Preferably top portions 151 and 152 of the one or more bafflesare at similar heights above the liquid collection tray so that the topplate 150 can be positioned in close proximity or contacting the topportions 151 and 152 to provide a generally enclosed mixing channel 60.The top plate 150 may be supported, at least partially, on the bafflesor it may be supported by other structure. In this respect, flanges maybe provided at the top portions 151 and 152 to support and/or attachedthe top plate.

As illustrated in FIGS. 1-3, by one aspect the outer wall 45 includes abaffle 155 extending about a center portion of the reactor 5 and spacedfrom the reactor walls. The inner wall 65 may be formed by anotherbaffle 160 adjacent to or contacting an inner surface of the outer wall45 and extending therefrom. It should be noted that each baffle may beformed from a single piece of material or two or more pieces of materialjoined together. By another aspect, as illustrated in FIG. 4, the outerwall 45 is positioned in close proximity to the reactor wall and abaffle 165 extends in an inward spiraling pattern toward the centerportion 153 of the reactor so that the baffle 165 serves as both theinner wall 65 and the outer wall 45 of the mixing channel 60. In yetanother example, as illustrated in FIGS. 5-8, the inner wall 65 may beformed from a baffle 170 separate from and spaced inwardly from a baffle175 forming the outer wall 45. In this approach, a separator baffle 180may separate the inlet end portion 80 from an outlet end portion 90 ofthe mixing channel 60. The separator baffle 180 may also serve as acontact surface to disrupt the swirling flow of fluid through the mixingchannel 60 before the fluid exits the mixing channel 60 and enters adistribution zone 190 of the mixing device 40 to facilitate separationand distribution of the vapor and liquid therefrom.

As mentioned previously, by one aspect, the mixing channel 60 caninclude an inwardly spiraling channel having an outer channel portion136 and an inner channel portion 137 positioned inwardly therefrom asillustrated in FIG. 4. An intermediate wall 191 may be positionedbetween the outer wall 45 and the inner wall 65 and may be formed of thesame or a different baffle from the one or more baffles forming theouter wall and the inner wall. Alternatively, the outer wall 45 can bepositioned in close proximity to the reactor wall as illustrated in FIG.4 with only a single mixing channel 60 to provide a wider mixingchannel.

By one aspect, the mixing system 30 further includes a distribution zone190 for distributing the fluid from the mixing device to a final vaporand liquid distribution tray 210. The distribution zone 190 may includean inlet portion 195 in fluid communication with the outlet end portion90 of the mixing channel 60. The distribution zone 190 may be generallycoplanar with the mixing channel 40 to reduce an overall height of themixing device 40 and the necessary interbed space required between thesuperior and inferior catalyst beds 10 and 15. As is typical, a finaldistribution tray 210 may be included below the mixing device, includingthe distribution zone 190, for providing high quality fluid distributionacross the inferior catalyst bed 15.

By one aspect, the distribution zone 190 includes one or more liquiddistributors 200 and one or more vapor distributors 205. In one approachthe liquid distributors 200 include openings 201 through a bottomportion of the distribution zone 190, for example a distribution zonebottom wall 215. The vapor distributors 205 may include one or moreopenings or vapor distribution chimneys 220. The vapor distributionchimney 220 includes an outer wall to restrict liquid flow through thechimney 220 and an upper opening to allow passage of vapor into anddownward through the chimney. The vapor distribution chimney 220includes a bottom opening 225 through the distribution zone bottom wall215 to allow vapor to pass downwardly therethrough. The distributionzone bottom wall 215 may be formed by a portion of the liquid collectiontray 35 extending below the distribution zone 190. By one aspect, themixing device 40 includes an annular mixing channel 60 and thedistribution zone 190 is positioned inwardly of the mixing channeltoward a center portion of the mixing device 40 with an inlet portion195 of the distribution zone 190 in fluid communication with the mixingchannel outlet portion 90.

By one aspect, the distribution zone 190 includes a liquid separationand distribution zone 230 as illustrated in FIGS. 2-4. The zone 230 maybe provided for separating liquid and vapor and distributing the liquidtherebelow. The zone 230 includes a channel 235 between an outer wall240 and an inner wall 245. The channel 235 may have an arcuate orannular configuration, or other suitable shape such as, for example,polygonal, and be positioned within the annular mixing channel 60. Inthis regard, the mixing channel inner wall 65 may form all or a portionof the channel outer wall 240 such that they are provided via a commonbaffle extending upwardly from the bottom wall and/or liquid collectiontray 35. A center vapor distribution chimney 255 may have a chimney wallthat forms the inner wall 245 of the channel. Without intending to bebound by theory, it is believed that as the fluid passes from the outletof the mixing channel 60 through the channel 235, the centrifugal forcesacting on the fluid as it swirls around the liquid separation channel235 causes the heavier liquid to separate from the vapor. The liquiddistributors 200 may be provided in the bottom wall 250 of the liquidseparation channel for so that the liquid is collected on the bottomwall 250 and distributed therebelow through the distributors 200.

As illustrated in FIGS. 1-3, by one aspect, a center vapor distributionchimney 255 may be positioned inwardly of the liquid separation channel235, and as mentioned above, form an inner wall of the liquid separationchannel 235. The vapor distribution chimney 255 may have a chimney wall260 extending above the bottom wall of the distribution zone bottom wall280. The distribution chimney includes an upper opening 265. The vaporchimney allows vapor to pass through the upper opening while restrictingthe flow of liquid therethrough. By one aspect, the vapor distributionchimney wall 260 extends upwardly only part-way to an upper wall of thedistribution zone, which may be a portion of the top plate or a separatewall. In this regard, the upper opening is provided between an upperportion of the distribution chimney wall 260 and the top plate 150. Asshown in FIG. 1, a spacer 270 may be provided above the chimney wall 260between the upper portion thereof and the top plate 150 to support thetop plate 150 thereabove. The spacer 270 may include one or more bars orother obstructions extending across the vapor chimney. In one example, agenerally X-shaped support 275 is positioned between vapor distributionchimney 255 and the top plate 150 to support the top plate 150. Thesupport may advantageously arrest the swirling flow of vapor in thedistribution zone 190.

According to another aspect, as illustrated in FIGS. 5-6, thedistribution zone 190 may include a bottom wall having a plurality ofliquid outlets 200 therein. The outlets 200 according to this aspect mayinclude a plurality of openings 201 through the bottom wall 280. Theopenings 201 for liquid flow are preferentially positioned at locationssuch that the liquid flows from these opening will not fall on to top ofthe distributors on the vapor-liquid distribution tray below. The bottomwall 280 may include a portion of the liquid collection tray 35. One ormore vapor distribution chimneys 220 may extend upward from bottom wall280. Each vapor distribution chimney 220 includes a vapor chimney wall290 and an upper vapor chimney opening 295 to restrict liquid fromentering the vapor distribution chimney 220. The vapor distributionchimney 220 encloses an opening 225 through the bottom wall 280 to vaporpasses through the opening and is distributed therebelow.

By one aspect, the liquid distributor bottom wall 280 forms a part of,or is at least generally co-planar with, the liquid collection tray 35.By another aspect, the bottom wall 280 may include a bottom tray 305offset below the liquid collection tray 35 as illustrated in FIG. 8. Thebottom tray may extend beyond the distribution zone 190 and below atleast a portion of the mixing channel 60. In this manner, the bottomtray 305 has a larger cross sectional area than is possible where thebottom wall 280 is co-planar with the liquid collection tray 35 toprovide for improved distribution therefrom. The expanded rough liquiddistribution zone will reduce liquid height gradient and liquid momentumflux on vapor-liquid distribution tray below. In this approach, thedistribution zone may include at least one opening 310 therethrough forpassing fluid to the bottom tray 305. By one aspect, the one or morevapor distribution chimneys 220 may extend up from the bottom tray 305,through the opening 310, and into the distribution zone 190. In thisregard, the bottom tray 305 may be spaced closely to the liquidcollection tray 35 while still providing for sufficient vapordistribution chimney wall height. In one example, the bottom tray isspaced between about 1 and about 5 in., in another example between about2 and about 4 in., and in yet another example between about 1.5 andabout 3 in. from the liquid collection tray 35. The distribution zonecan also be expanded into the bottom of mixing channel by raising thebottom of the mixing channel above the collection tray so that thedistribution zone is co-planar with the liquid collection tray.

As described previously, the mixing device 40 may include a top plate150 for providing a cover for the mixing channel 60 and/or distributionzone 190. The top plate 150 may be positioned near the bottom portion ofthe superior catalyst bed 10. It should be noted, that as used herein,the terms superior catalyst bed 10 and inferior catalyst bed 15, referrespectively to a catalyst bed system above the mixing stage and acatalyst bed system below the mixing stage, including supports and anyother parts of the catalyst bed system as are generally understood inthe art. The top plate 150 is preferably spaced from the bottom portionof the superior catalyst bed 10 so that it does not restrict the flow offluid descending therefrom. In this regard, descending fluid may contactand/or accumulate on an upper surface 306 of the top plate 150.

The top plate 150 may be configured to direct fluid in a desired manner.For example, the top plate may include weirs, an inclined surface, orother suitable features to direct fluid into a liquid collection zone 50or a liquid collection well 55. For example, referring momentarily toFIG. 4, an opening or space may be provided in the top plate 150 abovethe well 55 to allow fluid to pass therethrough.

According to one aspect, the system for providing a quench gas andmixing vapor and liquid between the superior 10 and inferior 15 catalystbeds includes a quench gas distributor 20 as illustrated in FIG. 2. Thequench gas distributor 20 may be positioned within the reactor walls andconfigured to dispense a quench gas toward fluid descending from thesuperior catalyst bed 10 to cool the fluid. The quench gas distributormay include a quench gas line 320 in communication with a quench gassource (not shown). The distributor may include a line, tube or pipe 325extending about at least a portion of the interior of the reactor 5.

As illustrated in FIG. 2, the quench gas distributor includes an arcuatepipe extending along the inner surface of the reactor wall between thereactor wall 6 and the mixing device 40. The pipe 325 includes aplurality of quench gas outlets or nozzles 330 for dispensing the quenchgas. The nozzles 330 may include any suitable outlet. By one aspect, thenozzles are positioned above an operation liquid level of the liquidcollection tray 35 so that liquid does not enter the nozzles. It hasbeen identified that hydrocarbon liquid entering the nozzles may hardenupon shutdown of the system when the hydrocarbon liquid cools and blockthe nozzles for future use. In one approach, the nozzles 330 arepositioned near a bottom portion of a superior catalyst bed 10. Thenozzles 330 may be configured to direct quench gas generallyhorizontally across the reactor to contact fluid descending from theupper catalyst bed 10, although the nozzles may also direct the quenchgas in other directions. In one approach, the nozzles are configured todirect fluid between the upper surface of the top plate 150 and thecatalyst bed. In this manner, intimate contact may be made between thequench gas and the descending fluids.

In another example, as illustrated in FIGS. 8-10, the quench gasdistributor 20 may be positioned to direct quench gas toward fluidsflowing from the top plate 150. For example, the quench gas distributormay be positioned to direct quench gas toward a mixing channel outerwall 45 to contact fluids cascading down from the top plate 150. In oneapproach, as illustrated in FIGS. 9 and 10, a weir 335 may be providedabout at least a portion of the top plate 150. The weir 335 may includean opening 340 so that fluids are directed through the opening 340. Thenozzles 330 may be configured to direct the quench gas toward theopening 340 to increase the amount of contact between the quench gas andthe fluids. The opening may include one or more apertures in the weir, agap in the weir, a low portion of the weir, or any other type of openingthat facilitates the flow of fluids therethrough. By one approach, theopening may include a low portion 345 of the weir 335 having anirregular upper portion, such as the zigzag pattern illustrated in FIG.11.

The quench gas distributor 20 may be positioned within the liquidcollection zone 50, as illustrated in FIGS. 5 and 6, or only extendabout a portion of the reactor as illustrated in FIGS. 2 and 8.

In another example, illustrated in FIGS. 5 and 6, the quench gasdistributor may be configured to direct quench gas downward towardliquid in the liquid collection tray 35. Also, as illustrated in FIGS. 5and 6, the quench gas distributor 20 may be partially or completelysubmerged in liquid on the liquid collection tray 35 to improvecontacting between the quench gas and the liquid on the liquidcollection tray 35. However, as discussed above, care should be taken sothat hydrocarbon fluid does not harden within the quench gas distributornozzles 330 when it is cooled.

By one aspect, a final distribution tray 210 may be positioned below themixing device 40 for final distribution of the liquid to the inferiorcatalyst bed 15. Suitable final distribution trays are commerciallyavailable, and one such tray is described in U.S. Pat. No. 7,506,861,which is incorporated herein, by reference in its entirety.

While this description has been provided with regard to specificembodiments, it is to be understood that this description should not belimiting to the disclosed embodiments, but it is intended to covervarious modifications and equivalent arrangements included within thescope of the appended claims.

Specific Embodiments

While the following is described in conjunction with specificembodiments, it will be understood that this description is intended toillustrate and not limit the scope of the preceding description and theappended claims.

A first embodiment of the invention is a method for fluid contacting ina downflow vessel, the method comprising collecting liquid on a liquidcollection tray; passing at least a portion of the liquid through aninlet of an enclosed mixing channel of a mixing device and downstreamthrough the mixing channel; and passing at least a portion of vaporthrough a vapor inlet of the mixing channel downstream of the liquidinlet and across the liquid stream flowing through the mixing channel tocontact the vapor and liquid in the mixing channel. An embodiment of theinvention is one, any or all of prior embodiments in this paragraph upthrough the first embodiment in this paragraph, wherein passing at leasta portion of the vapor through the mixing channel vapor inlet furthercomprises passing at least a portion of the vapor into a lower portionof the mixing channel into the liquid flowing through the mixingchannel. An embodiment of the invention is one, any or all of priorembodiments in this paragraph up through the first embodiment in thisparagraph, wherein passing at least a portion of the vapor through themixing channel vapor inlet further comprises passing at least a portionof the vapor obliquely downstream into the mixing channel to facilitatethe flow and contact of the liquid and vapor in the downstreamdirection. An embodiment of the invention is one, any or all of priorembodiments in this paragraph up through the first embodiment in thisparagraph, wherein passing at least a portion of the vapor through themixing channel vapor inlet further comprises passing at least a portionof the vapor through an upper chimney opening of a vapor chimneysurrounding the vapor inlet and passing the vapor downwardly through thechimney to the mixing channel vapor inlet. An embodiment of theinvention is one, any or all of prior embodiments in this paragraph upthrough the first embodiment in this paragraph, further comprisingpassing at least another portion of the vapor through a second vaporinlet of the mixing channel at a different downstream distance from theliquid inlet than the first vapor inlet and across the liquid streamflowing through the mixing channel to contact the vapor and liquid inthe mixing channel. An embodiment of the invention is one, any or all ofprior embodiments in this paragraph up through the first embodiment inthis paragraph, further comprising passing the other portion of thevapor through a second upper chimney opening of a second vapor chimneysurrounding the second vapor inlet before passing the other portion ofthe vapor through a second vapor inlet. An embodiment of the inventionis one, any or all of prior embodiments in this paragraph up through thefirst embodiment in this paragraph, further comprising passing at leasta portion of the liquid through the second upper chimney opening that islower than the first upper chimney and through the vapor inlet when aliquid level on the liquid collection tray exceeds a height of thesecond upper chimney opening. An embodiment of the invention is one, anyor all of prior embodiments in this paragraph up through the firstembodiment in this paragraph, wherein passing at least a portion of theliquid through the liquid inlet includes restricting at least a portionof vapor from entering through the liquid inlet by passing the liquidthrough an opening in a lower portion of the mixing channel outer wall.An embodiment of the invention is one, any or all of prior embodimentsin this paragraph up through the first embodiment in this paragraph,further comprising contacting the vapor and liquid in the mixing deviceby passing the liquid and vapor downstream through an annular passagewayof the mixing channel. An embodiment of the invention is one, any or allof prior embodiments in this paragraph up through the first embodimentin this paragraph, further comprising contacting the vapor and liquidwith a wall of a distribution zone to separate the liquid and vapor andto distribute the liquid and vapor below the mixing device. Anembodiment of the invention is one, any or all of prior embodiments inthis paragraph up through the first embodiment in this paragraph,further comprising swirling the liquid and vapor in a generally annularseparation zone to separate the liquid from the vapor. An embodiment ofthe invention is one, any or all of prior embodiments in this paragraphup through the first embodiment in this paragraph, further comprisingdistributing liquid below the mixing device by passing the liquidthrough an opening. An embodiment of the invention is one, any or all ofprior embodiments in this paragraph up through the first embodiment inthis paragraph, further comprising passing vapor through an upperopening of a vapor outlet chimney and distributing the vapor through thevapor outlet chimney.

A second embodiment of the invention is a method for fluid contacting ina downflow vessel, the method comprising passing vapor and liquid from asuperior stage of a downflow vessel to a mixing stage of the downflowvessel; collecting liquid on a liquid collection tray; passing at leasta portion of the liquid through an inlet of an enclosed mixing channeland downstream through the mixing channel; passing at least a portion ofthe vapor through a vapor inlet of the mixing channel downstream of theliquid inlet and across the liquid stream flowing through the mixingchannel to mix the vapor and liquid in the mixing channel; anddistributing the vapor and liquid to an inferior stage of the downflowvessel below the mixing stage. An embodiment of the invention is one,any or all of prior embodiments in this paragraph up through the secondembodiment in this paragraph, further comprising dispersing a quenchfluid into liquid collected on the liquid collection tray. An embodimentof the invention is one, any or all of prior embodiments in thisparagraph up through the second embodiment in this paragraph, furthercomprising dispersing a quench fluid above liquid collected on theliquid collection tray and toward fluid from the superior stage of thedownflow vessel. An embodiment of the invention is one, any or all ofprior embodiments in this paragraph up through the second embodiment inthis paragraph, further comprising directing liquid on the liquidcollection tray in one direction about an outer wall of the annularmixing channel to provide premixing of the liquid before passing theliquid into the mixing channel. An embodiment of the invention is one,any or all of prior embodiments in this paragraph up through the secondembodiment in this paragraph, further comprising passing vapor andliquid from an outlet of the mixing channel to a distribution zone anddistributing at least a portion of the liquid and vapor downward fromthe distribution zone. An embodiment of the invention is one, any or allof prior embodiments in this paragraph up through the second embodimentin this paragraph, further comprising passing vapor through an upperopening of a vapor chimney in the distribution zone and through thevapor chimney. An embodiment of the invention is one, any or all ofprior embodiments in this paragraph up through the second embodiment inthis paragraph, further comprising passing at least a portion of theliquid and vapor to a rough distribution tray spaced beneath the liquidcollection zone.

Without further elaboration, it is believed that using the precedingdescription that one skilled in the art can utilize the presentinvention to its fullest extent and easily ascertain the essentialcharacteristics of this invention, without departing from the spirit andscope thereof, to make various changes and modifications of theinvention and to adapt it to various usages and conditions. Thepreceding preferred specific embodiments are, therefore, to be construedas merely illustrative, and not limiting the remainder of the disclosurein any way whatsoever, and that it is intended to cover variousmodifications and equivalent arrangements included within the scope ofthe appended claims.

In the foregoing, all temperatures are set forth in degrees Celsius and,all parts and percentages are by weight, unless otherwise indicated.

The invention claimed is:
 1. A method for fluid contacting in a downflowvessel, the method comprising: collecting liquid on a liquid collectiontray; passing at least a portion of the liquid through an inlet of anenclosed mixing channel of a mixing device and downstream through themixing channel; and passing at least a portion of vapor through a vaporinlet of the mixing channel downstream of the liquid inlet and acrossthe liquid stream flowing through the mixing channel to contact thevapor and liquid in the mixing channel.
 2. The method of claim 1,wherein passing at least a portion of the vapor through the mixingchannel vapor inlet further comprises passing at least a portion of thevapor into a lower portion of the mixing channel into the liquid flowingthrough the mixing channel.
 3. The method of claim 1, wherein passing atleast a portion of the vapor through the mixing channel vapor inletfurther comprises passing at least a portion of the vapor obliquelydownstream into the mixing channel to facilitate the flow and contact ofthe liquid and vapor in the downstream direction.
 4. The method of claim1, wherein passing at least a portion of the vapor through the mixingchannel vapor inlet further comprises passing at least a portion of thevapor through an upper chimney opening of a vapor chimney surroundingthe vapor inlet and passing the vapor downwardly through the chimney tothe mixing channel vapor inlet.
 5. The method of claim 4, furthercomprising passing at least another portion of the vapor through asecond vapor inlet of the mixing channel at a different downstreamdistance from the liquid inlet than the first vapor inlet and across theliquid stream flowing through the mixing channel to contact the vaporand liquid in the mixing channel.
 6. The method of claim 5, furthercomprising passing the other portion of the vapor through a second upperchimney opening of a second vapor chimney surrounding the second vaporinlet before passing the other portion of the vapor through a secondvapor inlet.
 7. The method of claim 6, further comprising passing atleast a portion of the liquid through the second upper chimney openingthat is lower than the first upper chimney and through the vapor inletwhen a liquid level on the liquid collection tray exceeds a height ofthe second upper chimney opening.
 8. The method of claim 1, whereinpassing at least a portion of the liquid through the liquid inletincludes restricting at least a portion of vapor from entering throughthe liquid inlet by passing the liquid through an opening in a lowerportion of the mixing channel outer wall.
 9. The method of claim 1,further comprising contacting the vapor and liquid in the mixing deviceby passing the liquid and vapor downstream through an annular passagewayof the mixing channel.
 10. The method of claim 1, further comprisingcontacting the vapor and liquid with a wall of a distribution zone toseparate the liquid and vapor and to distribute the liquid and vaporbelow the mixing device.
 11. The method of claim 1, further comprisingswirling the liquid and vapor in a generally annular separation zone toseparate the liquid from the vapor.
 12. The method of claim 1, furthercomprising distributing liquid below the mixing device by passing theliquid through an opening.
 13. The method of claim 1, further comprisingpassing vapor through an upper opening of a vapor outlet chimney anddistributing the vapor through the vapor outlet chimney.
 14. A methodfor fluid contacting in a downflow vessel, the method comprising:passing vapor and liquid from a superior stage of a downflow vessel to amixing stage of the downflow vessel; collecting liquid on a liquidcollection tray; passing at least a portion of the liquid through aninlet of an enclosed mixing channel and downstream through the mixingchannel; passing at least a portion of the vapor through a vapor inletof the mixing channel downstream of the liquid inlet and across theliquid stream flowing through the mixing channel to mix the vapor andliquid in the mixing channel; and distributing the vapor and liquid toan inferior stage of the downflow vessel below the mixing stage.
 15. Themethod of claim 14, further comprising dispersing a quench fluid intoliquid collected on the liquid collection tray.
 16. The method of claim14, further comprising dispersing a quench fluid above liquid collectedon the liquid collection tray and toward fluid from the superior stageof the downflow vessel.
 17. The method of claim 14, further comprisingdirecting liquid on the liquid collection tray in one direction about anouter wall of the annular mixing channel to provide premixing of theliquid before passing the liquid into the mixing channel.
 18. The methodof claim 14, further comprising passing vapor and liquid from an outletof the mixing channel to a distribution zone and distributing at least aportion of the liquid and vapor downward from the distribution zone. 19.The method of claim 16, further comprising passing vapor through anupper opening of a vapor chimney in the distribution zone and throughthe vapor chimney.
 20. The method of claim 16, further comprisingpassing at least a portion of the liquid and vapor to a roughdistribution tray spaced beneath the liquid collection zone.